Diaphragm for phonographic reproducers



Aug. 10 1926. I G. w. MASTERSON ET AL DIAPHRAGM FOR PHONOGRAPHIC REPRODUCERS Filed March 25, 1925 Izz /enters,

' n h/244M 8'.

invention.

' the line 3-3 of F.i

Patented Aug. 10, 1926. 1,595,352 UNITED STAT ES PATENT OFFICE aroma WALTER uas'rnnson am) WILLIAM may "thorn, or 'ronom'o, onumo, sauna. nmmen roa rnonoemmc urnonucm'zs.

Application fled 1min 25, 19:5. semi m. 15,232.

tion as a diaphragm of such proportionate density has rovento be particularly sensitive to soun waves of varying frequency. This diaphragm is concentrically emhaped The invention relates to improvements in diaphragms for phonographic reproducers as described in the present specification and shown in the accompanying rawings which fo a t f th same. bossed, as at 2, to provide a cup-s The invention has for its object to proprotuberance on one side and radially extending from the same are four ribs, as at vide a phonographic diaphragm possessin certain features resulting in t e better an more natural reproduction of sound, particularly where tones either of hi h pitch or metallic quality are being repro need, in which event reproduction is inclined to develop or exa gerate metallic sound as a result'either o the inability of the diaphragmatic material to vibrate in harmony with t e frequency of the transmitted tonal wave, or by reason of the metallic resonance of the material-from which the diaphragm itself is formed. In accordance with the invention it has been found by experiment that when a thin celluloid sheet for use as a diaphragm is immersed in a dilute. solution of hydrochloric acid for, a suitable period of time it undergoes achange producing a diaphragm having a more' natural reproduction of sound. For example a circular diaphragm of uniform thickness corresponding to a ratio of .007 :1 to its diameter, concentrically embossed and provided with radial ribs for strengthening purposes, was immersed in a dilute solution of hydrochloric acid 'composed of one part of hydrochloric acid to ei ht parts of water. The diaphragm was su 'ected to the action of the solution fora period ofapproximately twenty hours and the resultin article gave a much better and more natura reproduction of sound particularly where tones of high'pitch were concerned and in addition e ectively eliminated the undesirable metallic resonance found in known diaphragms.

Referring to the drawings; Figure 1 is a side elevation of a dia hragm embodying the Figure 2 1s 3, such ribs being formed by embossing or. bein struck up as customary to procure this resu t. These ribs or veins are preferably spaced an equal distance apart and terminate s ort of the periphery. Centrally of the protuberance 2 is an aperture 4 for the purpose of connecting to the stylus bar of the reproducer.

. The diaphragm at any. stage in its course of manufacture is totally immersed in a solution composed of one part hydrochloric acid to eight parts of water for a period of approximately twenty hours. Said celluloid diaphragm 1 is maintained in the hydrochloric acid solution for a period of approximately twenty hours and although no apparent physical or chemical change takes place during the prolonged immersion there is a distinct tonal difierence in the diaphragms reproduction when same is compared with others which have not been treated by the process, although we are un1 85 able to advance a chemical or technical theory for the results obtained by this process.

In the use of celluloid for such a diaphragm it has been found that this material is rendered more responsive when the process hereinbefore recounted is undergone; whereas the ribbing or embossing of the diaphragm further adds to its usefulness by strengthening the same.

What we claim is 1. The process of treating a celluloid diaphragm, which consists in immersing it in a dilute solution of hydrochloric acid.

2. The process of treating a celluloid diaphragm, which consists in immersing it in a solution of one part of hydrochloric acid to eight parts of water.

3. 'The. process of treating a celluloid diaphragm, which consists in immersing it for a period of twenty hours in a solution of one part of hydrochloric acid to eight parts of water.

Signedat the city of Toronto, Canada, this 14th day of March 1925.-

GEORGE WALTER MASTERSON.

WILLIAM HARRY LLOYD.

an end view thereof. V Figure 3 is a cross sectional view taken on Like numerals o a reference indicate corresponding parts in each figure of the drawings.

In the drawings, the diaphragm 1 is constructed of a single piece of celluloid of a uniform thickness, such, preferably, corresponding to "a ratio of .007 1 to its iameter. It has been found in practice that this ratio between the thickness of the material and its diameter results in better sound reproduc- 

